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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
841

Optical measurement of shape and deformation fields on challenging surfaces

Nguyen, Tran January 2012 (has links)
A multiple-sensor optical shape measurement system (SMS) based on the principle of white-light fringe projection has been developed and commercialised by Loughborough University and Phase Vision Ltd for over 10 years. The use of the temporal phase unwrapping technique allows precise and dense shape measurements of complex surfaces; and the photogrammetry-based calibration technique offers the ability to calibrate multiple sensors simultaneously in order to achieve 360° measurement coverage. Nevertheless, to enhance the applicability of the SMS in industrial environments, further developments are needed (i) to improve the calibration speed for quicker deployment, (ii) to broaden the application range from shape measurement to deformation field measurement, and (iii) to tackle practically-challenging surfaces of which specular components may disrupt the acquired data and result in spurious measurements. The calibration process typically requires manual positioning of an artefact (i.e., reference object) at many locations within the view of the sensors. This is not only timeconsuming but also complicated for an operator with average knowledge of metrology. This thesis introduces an automated artefact positioning system which enables automatic and optimised distribution of the artefacts, automatic prediction of their whereabouts to increase the artefact detection speed and robustness, and thereby greater overall calibration performance. This thesis also describes a novel technique that integrates the digital image correlation (DIC) technique into the present fringe projection SMS for the purpose of simultaneous shape and deformation field measurement. This combined technique offers three key advantages: (a) the ability to deal with geometrical discontinuities which are commonly present on mechanical surfaces and currently challenging to most deformation measurement methods, (b) the ability to measure 3D displacement fields with a basic single-camera single-projector SMS with no additional hardware components, and (c) the simple implementation on a multiple-sensor hardware platform to achieve complete coverage of large-scale and complex samples, with the resulting displacement fields automatically lying in a single global coordinate system. A displacement measurement accuracy of ≃ 1/12,000 of the measurement volume, which is comparable to that of an industry-standard DIC system, has been achieved. The applications of this novel technique to several structural tests of aircraft wing panels on-site at the research centre of Airbus UK in Filton are also presented. Mechanical components with shiny surface finish and complex geometry may introduce another challenge to present fringe projection techniques. In certain circumstances, multiple reflections of the projected fringes on an object surface may cause ambiguity in the phase estimation process and result in incorrect coordinate measurements. This thesis presents a new technique which adopts a Fourier domain ranging (FDR) method to correctly identifying multiple phase signals and enables unambiguous triangulation for a measured coordinate. Experiments of the new FDR technique on various types of surfaces have shown promising results as compared to the traditional phase unwrapping techniques.
842

New formats for affinity selection of human cells

Sutar, Tina January 2015 (has links)
Despite recent advances in stem cell biology, immunotherapy and transplantation, substantial barriers still exist in the large-scale specific separation of a discrete population of human therapeutic cells from a cell suspension. The ideal purification technique should combine high cell purity, yield and function, with fast processing and affordability. Currently, fluorescence-activated cell sorting with flow cytometry (FACS) and magnetic activated cell sorting (MACS®) are the most used methods for cell separation and purification and have been employed extensively in molecular biology, diagnostic and cell sorting applications, because they are considered to be gentle, fast and scalable. However, these methods have several key disadvantages; they are invariably expensive, yield low log cell reduction (LCR) rates, and suffer from drawbacks when applied to niche cell populations, such as those requiring multiple tandem separation steps and/or involving combined positive and negative cell selection steps. To address this challenge, a new cell affinity selection system was developed. The selectivity is based on the reversible monomeric avidin biotin interaction and it is primary designed for positive selection. The initial studies were performed on flat, nonporous, glass coverslips and the technology was then successfully transferred on high grade smooth non-porous glass beads (with a diameter of 79.12 to 118.59 μm). The multi-step layer-by-layer deposition procedure culminating in dextran-coated supports bearing monomeric avidin was rigorously characterized and subsequently employed in packed bed chromatography experiments with human erythrocytes isolated from cord blood and B lymphocytes from cell lines. The developed affinity selection platform was highly selective, efficient and, most importantly, resulted in high yields, cell purity and viability comparable with MACS® technology. Additionally scale up is possible and could be easily transferred to another chromatographic matrix with the appropriate structure.
843

Development and Validation of a Computational Musculoskeletal Model of the Elbow Joint

Fisk, Justin Paul 01 January 2007 (has links)
Musculoskeletal computational modeling is a versatile and effective tool which may be used to study joint mechanics, examine muscle and ligament function, and simulate surgical reconstructive procedures. While injury to the elbow joint can be significantly debilitating, questions still remain regarding its normal, pathologic, and repaired behavior. Biomechanical models of the elbow have been developed, but all have assumed fixed joint axes of rotation and ignored the effects of ligaments. Therefore, the objective of this thesis was to develop and validate a computational model of the elbow joint whereby joint kinematics are dictated by three-dimensional bony geometry contact, ligamentous constraints, and muscle loading.Accurate three-dimensional bone geometry was generated by acquiring CT scans, segmenting the images to isolate skeletal features, and fitting surfaces to the segmented data. Ligaments were modeled as tension-only linear springs, and muscle were represented as force vectors with discrete attachment points. Bone contact was modeled by a routine which applied a normal force at points of penetration, with a force magnitude being a function of penetration depth. A rigid body dynamics simulator was used to predict the model's behavior under particular external loading conditions.The computational model was validated by simulating past experimental investigations and comparing results. Passive flexion-extension range of motion predicted by the model correlated exceptionally well with reported values. Bony and ligamentous structures responsible for enforcing motion limits also agreed with past observations. The model's varus stability as a function of elbow flexion and coronoid process resection was also investigated. The trends predicted by the model matched those of the associated cadaver study.This thesis successfully developed an accurate musculoskeletal computational model of the elbow joint complex. While the model may now be used in a predictive manner, further refinements may expand its applicability. These include accounting for the interference between soft tissue and bone, and representing the dynamic behavior of muscles.
844

A study of errors for 4D lung dose calculation

sayah, nahla K 01 January 2015 (has links)
To estimate the delivered dose to the patient during intra-fraction or throughout the whole treatment, it is important to determine the contribution of dose accumulated at different patient geometries to the overall dose. Dose mapping utilizes deformable image registration to map doses deposited on patient geometries at different times. Inputs to the dose mapping process are the irradiated and reference images, the displacement vector field, and a dose mapping algorithm. Thus accuracy of the mapped dose depends on the DVF and dose mapping algorithm. Dose mapping had been the subject of many research studies however, up to now there is no gold standard DIR or dose mapping algorithm. This thesis compares current dose mapping algorithms under different conditions such as choosing the planning target and dose grid size, and introduces new tool to estimate the required spatial accuracy of a DVF. 11 lung patients were used for this thesis work. IMRT plans were generated on the end of inhale breathing phases with 66 Gy as the prescription dose. Demons DVF’s were generated using the Pinnacle treatment planning system DIR interface. Dtransform, Tri-linear with sub-voxel division, and Pinnacle dose mapping algorithms were compared to energy transfer with mass sub-voxel mapping. For breathing phase 50% on 11 patients, tissue density gradients were highest around the edge of the tumor compared to the CTV and the PTV edge voxels. Thus treatment plans generated with margin equal to zero on the tumor might yield the highest dose mapping error (DME). For plans generated on the tumor, there was no clinical effect of DME on the MLD, lung V20, and Esophagus volume indices. Statistically, MLD and lung V20 DME were significant. Two patients had D98 Pinnacle-DME of 4.4 and 1.2 Gy. In high dose gradient regions DVF spatial accuracy of ~ 1 mm is needed while 8 to 10 mm DVF accuracy can be tolerated before introducing any considerable dose mapping errors inside the CTV. By using ETM with mass sub-voxel mapping and adapting the reported DVF accuracy, the findings of this thesis have the potential to increase the accuracy of 4D lung planning.
845

Radiation damage in protein crystallography : susceptibility study

Gerstel, Markus January 2014 (has links)
Protein structure models obtained from X-ray crystallography are subject to radiation damage. The resulting specific alterations to protein structures can be mistaken for biological features, or may obscure actual protein mechanisms, leading to misidentification or obscuration of biological insight. The radiation chemistry behind this site-specific damage is not well understood. Radiation damage processes progress in proportion to the dose absorbed by the crystal in the diffraction experiment. Doses can be estimated using existing software, but these assume idealised experimental conditions. To simulate complex diffraction experiments, including treatment of imperfect X-ray beam profiles and inhomogeneous dose distributions, a new program, RADDOSE-3D, was developed. RADDOSE-3D can be integrated into beamline software to provide convenient, more accurate, comparative, and publishable dose figures, also facilitating informed data collection decisions. There is currently no method to automatically detect specific radiation damage in protein structure models in the absence of an 'undamaged' reference model. Radiation damage research therefore generally relies on detailed observation of a few model proteins. A new metric, B<sub>Damage</sub>, is designed and used to identify and quantify specific radiation damage in the first large-scale statistical survey of 2,704 published protein models, which are examined for the effects of local environments on site-specific radiation damage susceptibility. A significant positive correlation between susceptibility and solvent accessibility is identified. Current understanding of radiation damage progression is mostly based on a few consecutive structure model 'snapshots' at coarse dose intervals. The low sampling rate considerably limits the ability to identify varying site susceptibility and its causes. Real space electron density data are obtained for crystals of different mutants of a RhoGDI protein with very high sequence identity, to determine sensitising and stabilising factors for radiation induced structural changes. Utilising a newly developed data collection and analysis protocol, these changes could be tracked with unprecedented time resolution.
846

Suzanne Lilar : configurations d'une image auctoriale

Cristea, Carmen 09 1900 (has links)
Cette thèse pose la question du positionnement identitaire difficile qui marque la trajectoire littéraire de l’écrivaine belge Suzanne Lilar (1901-1992). Le tiraillement vécu par l’écrivaine entre sa vocation artistique et la nécessité de préserver une image de soi conforme aux normes du milieu social dans lequel elle s’inscrit se reflète dans les scénographies construites par ses œuvres littéraires, mais également dans son discours réflexif et paratextuel ainsi que dans la manière dont son œuvre est accueilli par la presse de l’époque. Le premier volet de cette analyse s’attache à circonscrire la position occupée par Suzanne Lilar sur la scène littéraire belge, dont la proximité avec le centre parisien a toujours entretenu la menace de l’assimilation, et sur la scène de l’écriture féminine. Le deuxième volet de cette thèse porte sur l’analyse des scénographies construites par les textes de fiction et les textes à tendance autobiographique de Suzanne Lilar. Les doubles scénographies que donnent à lire ces œuvres montrent que la démarche esthétique de Suzanne Lilar, sous-tendue par le besoin de légitimation de son entreprise, est basée principalement sur la multiplication des perspectives et des moyens d’expression. Le dédoublement de la scène énonciative des récits, la mise en abyme de la figure auctoriale ainsi que le travail d’autoréécriture témoignent de la nécessité de se positionner dans le champ littéraire, mais également de la méfiance de l’écrivaine envers l’écriture littéraire. Le troisième volet de cette recherche analyse l’éthos et la posture que Lilar construit à l’aide du discours réflexif et paratextuel par lequel elle assoit sa légitimité sur la scène littéraire et sociale. Enfin, la dernière partie de cette thèse capte les échos de l’œuvre de Lilar dans la presse de son temps. L’image de l’auteure construite par les médias permet de placer Lilar au sein de l’institution et du champ littéraire, mais également au sein du groupe social dans lequel elle s’inscrit. L’accueil réservé à l’écrivaine par la presse de son époque semble suivre les fluctuations de la posture construite par l’écrivaine elle-même. Cela confirme l’hypothèse selon laquelle Lilar est une auteure qui a éprouvé de la difficulté à assumer pleinement son rôle. Le positionnement en porte-à-faux – dont témoigne la figure du trompe-l’œil qui définit sa poétique – semble avoir représenté, pour Lilar, la seule manière d’assumer l’incontournable paratopie créatrice. / This thesis investigates the difficult positioning of identity in Belgian writer Suzanne Lilar's literary trajectory. The conflict between the writer's art and her need to project an image consistent with her environment is reflected not only in the set-pieces of her literary works, but also in her essays and paratext, and in the way her works were received by the press of the day. The first part of the analysis describes Lilar's position in Belgian literary circles, whose proximity to the mainstream was always threatened by assimilation, and within feminist writings. The second part analyzes the storylines in her fictional and more biographical works. The parallel viewpoints in these works demonstrate that Lilar's aesthetic approach, which is based on the need to legitimize her enterprise, is based mainly on multiple perspectives and forms of expression. The duplication of the plot line in her stories, the mise en abyme of the author's voice, and the constant rewriting illustrate her need to make a place for herself in the literary landscape, but also her mistrust of literary writing. The third part of this research analyzes the ethos and position Lilar constructs through her essays and paratext, upon which she bases her literary and social legitimacy. The final part of the thesis reports on how Lilar's work was received in its day. The image of Lilar propounded by the media positioned her within the literary establishment and also within her own chosen social stratum. The press of the time viewed her as she variously presented herself. This corroborates the hypothesis that Lilar had trouble in fully assuming her role as a writer. Her presentation of herself as being out of step with society − in the trompe-l'oeil manner of her poetics − appears to have been the only way for Lilar to shoulder the displacement essential to her creative work.
847

Caractérisation 3D de l'hétérogénéité de la perméabilité à l'échelle de l'échantillon / 3D Chatacterization of Permeability Heterogeneity at the Core Scale

Soltani, Amir 21 October 2008 (has links)
L’objet de cette thèse est de développer des méthodologies permettant d’identifier la distribution spatiale des valeurs de perméabilité dans des échantillons de roches. Nous avons tout d’abord développé en laboratoire des expériences d’injection de fluide miscible très visqueux dans des échantillons initialement saturés par une saumure peu visqueuse. Pendant l’injection, l’évolution au cours du temps de la pression différentielle entre les deux faces de l’échantillon a été enregistrée par des capteurs de pression. En outre, des mesures scanner ont fourni une carte 3D de la porosité ainsi que des cartes 3D décrivant la distribution spatiale des concentrations dans l’échantillon à différents temps. Nous avons mis en place une méthode d’interprétation donnant directement le profil 1D de la perméabilité le long de la direction d’écoulement à partir de la pression différentielle mesurée au cours du temps. Cette méthode a été validée numériquement et expérimentalement. Puis, afin d’affiner la description de l’agencement des valeurs de perméabilité dans l’échantillon, c’est à dire d’obtenir un modèle 3D de perméabilité représentatif de l’échantillon, nous avons développé une méthodologie itérative de calage des pressions et des concentrations. Cette méthode passe par deux étapes : une optimisation simple pour capturer l’hétérogénéité dans la direction de l’écoulement et une optimisation complexe pour capturer l’hétérogénéité transverse. Cette méthode a été validée à partir de tests numériques. La méthode a été appliquée à deux des expériences d’injection de fluide visqueux. Nous avons pu alors déterminer des modèles de perméabilité capables de reproduire assez bien les données de pression et de concentration acquises pendant l’injection / The objective of this study is to develop new methodologies to identify the spatial distribution of permeability values inside the heterogeneous core samples. We developed laboratory viscous miscible displacements by injecting high viscosity glycerin into the core samples initially saturated by low viscosity brine. The pressure drop across the samples was measured as a function of time until breakthrough. Meanwhile, CT scan measurements provided a 3D porosity map plus several 3D maps of concentration distribution inside the core samples at different times. A simple permeability mapping technique was developed deducing a one-dimensional permeability profile along the flow direction from the measured pressure drop data. The method was validated with both numerical and laboratory experiments. To go beyond one-dimensional characterization of permeability into cores, we developed an iterative process for matching pressure and concentration data. This method consisted of two steps: a simple optimization for capturing the permeability heterogeneity along the flow direction axis and a complex optimization for capturing transversal permeability heterogeneities. The methodology was validated by numerical data. It was also applied to the data collected from two laboratory viscous miscible displacements. We showed that the final 3D permeability models reproduce well the measured pressure drop and concentration data
848

Kraniometrická studie středoevropských populací bělozubek Crocidura suaveolens a C. leucodon (Mammalia: Soricomorpha) / Craniometric study of Central European populations of the white-toothed shrews Crocidura suaveolens and C. leucodon (Mammalia: Soricomorpha)

Milerová, Petra January 2014 (has links)
Interspecific and intraspecific size variability of the skull, mandibles and teeth of the lesser white- toothed shrew Crocidura suaveolens and the bicolored white-toothed shrew C. leucodon was studied on material of 350 skulls and 465 mandibles of white-toothed shrews obtained by analysis of the barn owl pellets originating from four regions in the Czech Republic and one region in the southern Slovakia. C. suaveolens was present in all regions under study, while sympatric C. leucodon occurred in three regions only. In total, 21cranial and dental measurements and 4 mandibular measurements were investigated. It was found that the most reliable measurement enabling discrimination between skulls of both species in the whole studied material is the lenght of the lower dental row. If skulls of both species were evaluated separately for each area of their sympatry it was possible to use also the distance between second molars M2 and the width of premolar P4 . Skulls of these two species can also be distinguished by bivariate graphs using the length and width of premolar P4 and the palatal length. We studied relationships between cranial measurements of both species and geoclimatic factors such as longitude, latitude, mean annual temperature and mean annual percipitation. It was found that variability of...
849

Hodnocení stresové relaxace směsí laktosy a hydrogenfosforečnanu vápenatého určených k přípravě tablet s theofylinem. / The evaluation of stress relaxation of lactose and calcium hydrogen phosphate mixtures intended for the preparation of tablets with theophylline.

Le, Thanh Tra January 2016 (has links)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of: Pharmaceutical technology Consultant: Mgr. Petra Svačinová, PhD. Student: Le Thanh Tra Title of Thesis: Evaluation of stress relaxation of mixtures of lactosum and calcii hydrogenphosphate for preparation tablets with theophylline This thesis studies viscoelastic behavior of fillers and tensile strength of tablets with theophylline. Used material are described in theoretical part: Laktosum SpheroLac 100, microcrystalline cellulose Comprecel 102, calcium hydrogenophosphate anhydrate Di-Cafos A150, calcium hydrogenophosphate dihydrate Di-Cafos D160, theophylline and magnesium stearate. Thesis also describes the stress relaxation test, methods of evaluation and it's application. Experimental part evaluates viscoelastic behavior and tensile strength through the test of stress relaxation with maximal compression force 10 kN and dwell time 180 s. The tensile strength of tablets is also evaluated. Experimental part evaluates parameters of elasticity Ai and plasticity Pi, which were obtained from the test of stress relaxation. It evaluates effect of different fillers on these parameters. The highest values were measured at mixtures E (Spherolac 100 a Comprecel 102), further at mixtures D (Spherolac 100 a Di-Cafos A150) and...
850

Rovnice sypání granulátu sorbitolu s přídavkem stearanu hořečnatého. / Flow equation of sorbitol granules with addition of magnesium stearate.

Damborský, Ondřej January 2016 (has links)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of: Pharmaceutical technology Consultant: Doc. PharmDr. Zdeňka Šklubalová, Ph.D. Student: Ondřej Damborský Title of Thesis: Flow equation of sorbitol granules with addition of magnesium stearate. The aim of this thesis is to study particulate built and consolidation properties of the granulate prepared by wet granulation of sorbitol and it's size fractions in the range of 0,2 - 0,8 mm and it's influence of adding lubricate magnesium stearate 0.5% and 1.0%. The properties were studied by the angle of repose, the three kinds of bulk density, tap density, the Hausner ratio. The granules showed adequate to good flow properties. The addition of magnesium stearate flow increases the rate through the granulate sorbitol. Mass flow rate through the orifice the conical hopper of the test depending on the particle size and hole diameter were monitored. With increasing particle size the rate of pouring decreases, while the diameter of the hole had the opposite effect. Dependence of the flow rate to the average of the opening of the hopper was modeled by a power equation Jones-Pilpel. When using the current parameters with accuracy reverse estimate of the flow rate ranged between approximately 2 - 4%.

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